The invention relates to the general field of telecommunications.
It relates more particularly to a solution that makes it easy for a called user to filter communications addressed to that user, and in particular to filter undesirable communications.
The present invention has a preferred, but non-limiting, application in the context of communications sent to users by call centers (e.g. after-sales service centers, call centers undertaking commercial campaigns targeting users, etc.).
Such call centers can be called by users themselves, e.g. in the event of problems involving equipment or services to which the users have subscribed. By way of example, a user may call a call center of a telecommunications operator in order to complain about a malfunction of a telephone installation. If the problem can be solved simply, it might be corrected directly during the call; otherwise, the call center may need to call the user back the same day or in a few days.
Call centers can also contact users at their own initiative, e.g. in order to promote or sell new products or services, or to propose commercial rendezvous, etc. In a “generic” call center that makes calls on behalf of third parties (e.g. a bank), regulations in France require that the number displayed on the terminal of the called user is a number that makes it possible to reach the third party (in the above example the bank) on whose behalf the call center is calling the user.
In the two situations described above, the called user has no guarantee nor “technical” means for verifying that the person contacting the user on behalf of the call center is indeed a representative of that call center.
Specifically, the calling number displayed on the terminal of the called user is a number that is not certified and that can easily be usurped. An identifier is said to be certified when that identifier is established and guaranteed by a trusted entity (e.g. the network operator or some other trusted authority). The calling number is inserted by the caller's terminal or more generally telecommunications equipment (e.g. a private automatic branch exchange (PABX)) at the calling end, and it is conveyed in transparent manner in a call signaling field from end to end by the network(s) through which the call passes between the caller and the called party. For example, with networks implementing session initiation protocol (SIP), the non-certified identifier is conveyed in the SIP FROM field of the SIP INVITE message. The call signaling does indeed convey a certified identity as added by the caller's network (in the example of the SIP protocol, this certified identity is to be found in the SIP P-Asserted-Id field of the INVITE message), however the certified identity is not displayed on the terminal of the called user. It is reserved for billing procedures, for legal interceptions, for enabling the caller to mask the caller's number, etc.
Because a non-certified identifier is displayed on the terminal of the called user, certain ill-intentioned callers do not hesitate to usurp the identities of call centers and to pass themselves off as agents of those call centers. A frequently-encountered situation is as follows: a “fake” agent calls a user, e.g. while pretending to be an agent of the user's bank and putting the number of that bank in the non-certified identifier of the call signaling (e.g. in the SIP FROM field). The called client then sees the client's own bank number displayed and is thus made to feel confident, and might give away sensitive information to the fake agent.
Similar situations can also affect the clients of telecommunications operators who can have their client accounts usurped.
In the face of the multitude of communications channels now in use by call centers (fixed or mobile telephone, short message service (SMS) type messages, instantaneous or electronic messaging, etc.), and in the face of the multiple potential usurpers, these situations are becoming and more frequent. There thus exists a need for reliable technical means in compliance with the regulations that are in force to enable called users to be sure of the identity of the parties calling them when they receive calls from numbers associated with their call centers, so as to enable them to filter malicious calls.